A representative crosslinking monomer is ethyleneglycoldimethacrylate or 1,4-butanedioldiacrylate. A representative pigment is iron oxide black or iron oxide brown.
The colorant-containing composition may include other components. A first example is a hydrophilic comonomer, such as 2-hydroxyethylmethacrylate. A second example is a hydrophobic comonomer, such as 2-butoxyethylacrylate. A third example is ethyl lactate. Additionally, these compositions will generally include a polymerization initiator.
The contact lens substrate can be made of any known hydrophilic copolymer. A preferred copolymer is hilafilcon B, which is the polymerization product of a monomer mixture comprising 2-hydroxyethylmethacrylate, N-vinylpyrrolidinone, ethyleneglycoldimethacrylate, and allylmethacrylate.
Preferably, the colorant-containing composition has a concentric ring shape on the surface. Most preferably, the concentric ring essentially conforms to a position of a human iris when the contact lens is placed on the eye, and may have a larger outer diameter than a human iris.